Last February, in a high-school gym in Annandale, nearly 100 volunteers from Deloitte sat at tables preparing tax returns. Every now and then, a client would hug a Deloitte accountant and start to cry.

It was Community Tax Assistance Day, and people who could not afford to have their tax returns prepared for them were having them done for free. Without that help, many would not have gotten refunds they were owed—sometimes thousands of dollars.

On any given day, Washingtonians are out volunteering: painting schools, feeding the homeless, ushering at theaters.

But in this city of highly educated professionals, there’s a kind of volunteering that especially motivates some people: opportunities that use their job skills, whether marketing or accounting or Web design.

A study released by the Corporation for National and Community Service found that professionals are more likely to stick with volunteering if the task makes use of their education or expertise.

“When volunteers use their skills, they feel more valued,” says Jamie Hartman of the Taproot Foundation, which connects professionals with nonprofits.

“It’s not to say planting trees or tutoring kids isn’t rewarding; it’s very rewarding,” says Emily Rothberg, head of Deloitte’s community involvement in this region. “But if you really care about the community, why not do the thing you do best?”

Capital One, the McLean-based financial-services giant, has a program in which teams of talent—in IT, law, finance, human resources, and more—assist nonprofits. Smaller firms do pro bono, too—creating brochures, building databases, sitting on boards.

The last thing some people want to do in their free time is what they do all day at work. Still, physicians and dentists have for years provided free care to those in need, and pro bono is a tradition in law firms.

“Lawyers who are using their skills volunteer more than any other profession,” Hartman says. Taproot is hoping to expand the pro bono ethic throughout other occupations. The trick is doing skills-based volunteering right.

“Fifty percent of pro bono projects fail,” Hartman says. Taproot and other groups try to improve those odds by matching a volunteer’s skills with the needs of a charity and making sure projects are well structured and have a clear time commitment, say three months.

What follows is a list of organizations that match skilled professionals with charities. Professional associations also maintain listings of opportunities.

Cultural Alliance of Greater Washington’s Business Volunteers for the Arts, cultural-alliance.org/programs/bva.html. Brings together arts groups and volunteers who have skills in finance, marketing, information technology, human resources, and development.

DC Appleseed, 202-289-8007; dcappleseed.org. Volunteer lawyers, businesspeople, and other professionals work on policy issues facing the city, including healthcare, education, economic development, and the environment.

Greater DC Cares, 202-777-4454; dc-cares.org/pro-bono.html. Its Pro Bono Consulting Program pairs people with experience in finance, human resources, marketing, communications, organization development, and technology with more than 400 charities.